Can you bake materials (not textures) in Blender?
You cannot bake the "node tree" itself to use it directly in the shader node editor of another program like Unity, Unreal engine or Substance painter. 

But you can bake the resulting maps (albedo, roughness, metallic, alpha value...) and then apply them in another software as if they were regular textures.

See : for texture baking 
How do I bake a texture using Cycles bake